The present invention relates to a method of connecting a flat-type electric wire with a connector terminal in the field in which high reliability is required, such as for example, the inside of an information apparatus such as a computer or the like, between such apparatuses, or electric or control parts of a car, and so on.
As a method of connecting a flat-type electric wire with a connector terminal with high reliability, a conventional method has been employed in which a terminal portion of a flat-type electric wire is subjected to terminal treatment so that at least one surface of the conductor of the terminal portion is exposed, the conductor of the terminal portion is sandwiched between two upper and lower metal plates partially connected to each other, and the conductor and the metal plates are spot-welded to each other.
The state in which the spot-welding described above is being carried out, is as shown in FIG. 2 in which a current is made to flow between upper and lower electrodes 4 and 5 so that a conductor 8 of a flat-type electric wire 2 and a metal terminal 1 sandwiching the conductor 8 are fused to each other at a projection portion 10. In the case where an insulator 9 is remained on one surface of the flat-type electric wire at its terminal portion (because if insulation is removed from both surfaces to leave only the conductor, a trouble such as disorder in pitch or the like is apt to happen, terminal treatment is carried out so as to expose only one surface of the conductor), a current, for example, of about 300-500 A is first made to flow so as to fuse the insulator at the terminal portion, and then a large current of 1-1.5 KA is made to flow so as to fuse the conductor with the metal terminal.
In order to apply such spot-welding successively to a number of products as a part of a manufacturing process and in order to carry out the spot-welding always stably to all the products, it is necessary to always stabilize the contact resistance between the conductor of the flat-type electric wire and the metal terminal. It is a countermeasure to provide the projection portion 10 shown in FIGS. 1 and 2. Even if such a countermeasure is taken, however, the contact resistance is apt to become unstable because of variations in height of a caulked portion 7 of the terminal shown in FIGS. 1 and 2 or variations in thickness of the flat-type electric wire. Particularly in the case where the contact resistance becomes large, there happens a disadvantage that an overcurrent flows into a terminal root portion 11 shown in FIGS. 1 and 2 to burn off the terminal root portion.